Porsche 959 “Gruppe B” – Group B Prototype

Published on: Jan 20, 2016 @ 20:32
Originally Published in: 2014 (old website)
(C) Jay Auger - website owner & author
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PORSCHE 959 “Gruppe B” – Group B Prototype


As soon as it was officially announced in 1980, the new Group B class went under scrutiny from famed German sportscar maker Porsche since it promoted faster and cheaper technical innovations. Peter Schutz, Porsche’s CEO of the time, ordered the “Gruppe B studie” to reevaluate the company’s motorsport future under the new sporting regulations.



In the late 1970’s, Ernst Fuhrmann (Schutz’s predecesor) strongly believed that Porsche’s future laid with the 928 model and had stopped further development of the company’s 911 flagship icon. The first Group B concept to come out of this study is believed to have been based on the 928, which would have sported aerodynamic improvements with an all new Kevlar body, a twin-turbo V8 engine and most importantly four-wheel drive. However, when Schutz took over he firmly reiterated that most people identified the image of the marque with the classic 911. As such, the 928 idea was immediately scrapped in favour of a new concept based on the 911.

One of the biggest challenges of the new Group B regulations was the minimum homologation requirement of 200 road cars to be built within in 12 months. It was clear to Porsche’s engineers that only a true race car could be competitive. However, there was no way that Porsche could find that many customers for such a specialised and brutal car so the project was put on hold to see if Group B circuit racing would ever take off (“silhouette” racing had stopped after the absorption of Group 5 into Group B thus ending the 935 glory days in 1982).

Porsche 935.jpg
Porsche 935 – Group 5

Meanwhile, the focus was put on the 956 Group C racer and developing a quicker solution for Group B rallying in the form of the twenty 911 SC/RS “evolution” cars. However, Group B rallying proved to skyrocket the popularity of the sport in the World Rally Championship (WRC) in a very short amount of time, with the likes of Audi and Lancia campaigning cars that were packed with their latest technologies.

As such, a Porsche Group B car was considered once again in early 1983. Porsche’s competition department came to the conclusion that the technologies required for modern rally cars also applied to circuit racing and could later be used on future production cars. The “Gruppe B” project was approved and the engineers immediately went to the drawing boards.


Design on the 959 started in the spring of 1983 and actual production was planned to begin early in 1985. While the initial concept of the car was meant purely for creating the best race car, it soon shifted to being for the best road-legal car that could excel in both departments. Due to its very high technology showcase conception, the designers soon estimated that the 959 would be the most expensive road-going Porsche ever built. However, by using the basic 911 chassis, the Porsche engineers had a quick starting point to begin developing a physical prototype.


Much of the early work focused on the four-wheel drive system, which the Porsche engineers had very limited experience with. Various systems were tested in combination with different suspension types. The hardware of the Porsche four-wheel drive system was fairly straightforward but the real quantum leap came in with use of electronic controls. The system was equipped with a computer that controlled the amount of drive to the front wheels, through a ‘PSK’ clutch fitted between the gearbox and the front differential. It compensated, for example, for the weight shift during acceleration. The driver would also be given four settings to manually control the power sent to the front wheels in extreme conditions like ice or snow.

The engineers also found that the four-wheel drive system worked best when coupled with a double-wishbone front suspension instead of the McPherson struts normally found on a 911.  Each side was fitted with twin coil springs over damper units to ensure that the front wheels had traction at all times and under all conditions. The rear suspension also consisted of double wishbones but with just one coil/damper combination and an additional damper on each side. With its potential rally and circuit careers in mind, the 959 chassis was equipped with four different mounting points for each wishbone to adjust the ride height. The pressure in the dampers could be adjusted from the cockpit by the driver. Other advanced technologies were being developed such as anti-lock brakes (ABS) and tire pressure monitoring.

Porsche was eager to showcase a preview of the company’s new Group B contender at the upcoming Frankfurt (IAA) Auto Show in September of 1983. From the first observations, apart from the shell, very little from the 911 body was seemingly carried over. The prototype 959s can be easily differentiated from the latter production version by its use of “turbo / wheel fan” (vented disc) type wheels:

959 in Prototype Version

For its circuit racing ambitions, light weight and low drag were top priorities for the designers and to complicate things further, the Porsche 911 overall shape had to be retained for obvious commercial reasons. Key features of the original 911 launched exactly 20 years earlier were implemented into a much wider and smoother bodywork. The designers had hoped to get away with a wingless design but wind tunnel tests showed that the rear end could not do without. To suit the smooth design of the car, the engineers went for an elegant yet functional integrated rear wing. Thanks to a fully enclosed undercarriage the drag figure was kept down to a very aerodynamic 0.32 Cd.

Continuing on the tradition of the 911, the engine obviously had to be an air-cooled flat-6 but it ended up being distinctly different from any engine ever fitted in a 911 road car. In fact, it shared many components with the unit of the very successful 956 race car. The main departure from the 911 design were the cylinders that now featured twin overhead camshafts and four valves per cylinder. The addition of two sequential turbos boosted the power to 450 BHP. Final displacement was chosen at 2849 cc to efficiently maximise the particular Group B engine class (3989 cc with the forced induction 1.4 multiplication factor) that engineers had planned for the car to run in.

However, there was a flaw in the initial design of the engine: vibrations from the camshafts had a negative effect on the chains driving them. The solution was a twin-chain setup but that meant that several parts now had to be recast. The engine problems had caused the introduction date of the production car to be delayed several times.


To ensure that the 959 met all the quality standards expected from the Porsche name, 21 pre-production “vorserie” prototypes were built and made subject to extensive testing. These can be easily differentiated from other 959s by their rally style auxiliary lamps added to the front of the car:

The 1985 International Automobil-Ausstellung (auto show) in Frankfurt was set as the new launch date of the 959 road car with deliveries expected to begin in the fall of the next year. The final specifications included a fully appointed interior with luxurious leather seats, electric windows and air-conditioning. That was quite unlike the other Group B homologation specials and clearly showed where Porsche’s priorities had shifted. The price had almost tripled from the initial estimate. Nevertheless, Porsche received as many as 1,600 customer inquiries from the auto show. Eventually, 250 orders were accepted after the clients placed a substantial down payment. Due to the time delays and high cost of the project, Porsche refused to waste additional resources to adapt the car to the very strict emission and higher safety standards upheld in the United States and Canada.

Although the car had created a lot of initial excitement, some insiders felt like the 959 should still prove itself in racing. After all, it was why the project had originally started. Jackie Ickx, a former factory Porsche driver, convinced Porsche management that “Rally/Grand Raid” type events, like the increasingly famous Paris-Dakar rally, would be an excellent venue to demonstrate the 959’s capabilities. Thus, Porsche ran the 1984 African desert endurance events with three 911s modified to basic 959 specifications, albeit with a largely detuned 232 BHP engine, and with a simplified, purely mechanical version of the four-wheel drive system, but came home victorious nonetheless – proving the project’s worth.

Encouraged by the results of 1984, three “real” 959s made their first appearance in the Dakar’s Sahara desert in 1985, now fully equipped with Porsche’s high technology arsenal. However, it was a year to forget; two 959s were involved in accidents, while the third suffered from a broken oil pipe. Despite the lack of success, Porsche decided to return for the 1986 event with enhanced preparations. They again fielded three 959s, but the turbo boost was lowered to cope with Africa’s low octane fuel, which saw the power decrease to 390 BHP. It was to be Porsche’s year as the three cars finished first, second, and sixth.

Porsche was obviously satisfied and decided to continue developing a second racing derivative of the 959. Officially known as the 961, it was directly aimed at circuit racing while sharing a close visual and technical resemblance to the 959. The 961 was a widebody circuit racer destined to compete in Porsche’s home away from home; Le Mans. The 961’s engine was further tweaked to produce a hefty 640 BHP and the car became the first four-wheel drive car to race at Le Mans in 1986.

The 961 scored what can be considered as the first and only “Group B circuit win” by coming in victorious of its prototype class, all while finishing an incredible 7th overall. Later entered in the IMSA GTX class for experimental cars, Porsche had hoped this would sell copies of the new racer to the United States but, due to its very high price, they failed to get a single order.

Porsche had thus proven the potential of the 959/961 both for rallying and for racing. However, by then, news of the Group B ban were made official and this would ultimately put a premature end to any further motorsport ambitions for the 959/961.

The 959 would subsequently be produced over the 200 units required for Group B homologation but Porsche decided not to apply for the official documentation papers although the FISA was still accepting post-ban homologation requests. Porsche thus saw no point in performing the tedious task of homologation since the project had already far exceeded initial budget. However, this decision can be criticised since the 959 was THE company’s flagship model synonymous with Group B from the very beginning.

After much production delays, the first 959 road cars were finally shipped out in 1987. However, some purists considered them far too civil to be considered a real road / race car hybrid. As such, a final version of the car was developed late in 1987: the 959 “Sport” (959S). It was an extensively lightened version of the “standard” or “Komfort” model by stripping luxury items like electric windows, leather power seats, rear seats, air-conditioning, as well as removing the adjustable ride height control suspension. A total of 100 kg was hence shaved off the weight of the original 959. There was also an optional 530 BHP upgrade offered with the “Sport” model. These cars can be quickly visually differentiated from the “Komfort” model by their lack of a passenger side mirror:


In an ingenious attempt to make the 959 available for its dedicated American customers, Porsche developed a second version of the “Sport” model (also known as the “Sport II”) – fitted with a roll cage and stripped of its adjustable dampers and was marketed as a pure racing car. This meant that the strict US emissions (EPA) and safety standards should in theory not apply. However, the American officials saw through the ploy and sent the first batch of seven cars back to Germany.

Several examples have since been successfully imported to the United States under the 1999 “Show and Display” law, which was heavily lobbied for by a few well-funded gentlemen. The original EPA ruling that outlawed the 959 expired in 2010 thus allowing the cars to be freely imported into the country ever since. Canepa Motorsports has subsequently developed an engine package that increases the power output while meeting the strict emission standards of California.


At the time of its launch, the 959 held the record as the fastest production car with a top speed of 197 mph / 317 kph until it was beaten shortly thereafter by its future arch rival: the Ferrari F40 (201 mph / 324 kph). The duo is credited with the “supercar renaissance” – a trend that continues to this day. While the F40 proved to be a financial success for Ferrari, Porsche actually lost money on each 959 sale due to its very high technology, road and race design, lower production volume, and sheer project cost.

Although the 959 never actually competed in Group B as a fully fledged homologated car, it nonetheless helped firmly secure Porsche’s place in automotive history as the 959 is considered to be the first true high tech supercar and forerunner of all others to come. As such the car is very coveted by Porsche and sports car collectors, with many examples recently sold at auction for more than 1 million dollars – sometimes double that amount.


Class Sports / Supercar four-wheel drive coupe
Production 1986~1988 (337 units) Assembly: Germany
Type Type 959/50 B6, H-6, DOHC 24v, gas rear, longitudinal
Displacement 2849 cc WRC (x1.4) = 3989 cc
Compression Ratio 8.3:1
Output Power – Torque 444 HP @ 6500 rpm 369 lb-ft @ 5500 rpm
Materials block: aluminum cylinder head: aluminum
  • twin sequential turbos
  • air/air intercoolers
  • Bosch fuel injection
  • boost: 14.5 psi
Ignition Bosch Motronic electronic
Lubrication System
Cooling System air cooled cylinders / water cooled heads
Type “PSK” four-wheel drive 6-speed manual gearbox
Gearbox Ratios
Differential Ratios electronic ratio control (default F40/R60 – up to F20/R80 or F50/R50)
Type 930-derived steel monocoque chassis, aluminum panels, fiberglass reinforced kevlar bonnets, polyurethane roof
Front Suspension
  • 4-way adjustable double wishbones, dual coil springs over fully adjustable shock absorbers, anti-roll bar
Rear Suspension
  • 4-way adjustable double wishbones, coil springs, fully adjustable dual shock absorbers, anti-roll bar
Steering System rack & pinion
  • Front & Rear: cross drilled & vented discs
  • Front: 322 mm rotors
  • Rear: 308 mm rotors
  • dual circuit with servo
  • anti lock system (ABS)
length: 4260 mm (167.7 in) width: 1839 mm (72.4 in) height: 1280 mm (50.4 in)
wheelbase: 2273 mm (89.5 in) front track: 1504 mm (59.2 in) rear track: 1549 mm (61.0 in)
Rims – Tires
  • Center locking magnesium wheels
  • Front: 17″ x 8.0″
  • Rear: 17″ x 9.0″
  • Front: 235/45VR-17
  • Rear: 255/40VR-17
Curb Weight
  • “Komfort” 1450 kg (3200 lb)
  • “Sport” 1350 kg (2975 lb)
Bias: –
  • “Komfort” 3.2 kg/hp (7.1 lb/hp)
  • “Sport” 3.0 kg/hp (6.6 lb/hp)
Fuel Tank
Drag Coefficient 0.32



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